Fix typos

Found via `codespell-q 3`

README.md

@@ -29,7 +29,7 @@ Pyembroidery fully meets and exceeds all of these requirements.
 * It supports all the core commands where that format can use said command as well as FAST and SLOW for .u01.
 * SEQUINS work in all supported formats (.dst) that are known to support sequins. Further it supports SEQUIN to JUMP operations on the other formats.
 
-Though previously mandated support for Python 2.7, this support was dropped at the end of life for that version. It is highly recommended that you upgrade. A `python27` branch is availible but that branch was merely forked from when the version was supported.
+Though previously mandated support for Python 2.7, this support was dropped at the end of life for that version. It is highly recommended that you upgrade. A `python27` branch is available but that branch was merely forked from when the version was supported.
 
 
 ## Philosophy
@@ -202,7 +202,7 @@ Prints out a workable CSV file with the given data. Starting in 1.3 the csv patt
 
 
 #### Reading/Writing to JSON:
-Saves the pattern as a JSON object. This is intended to be useful as an interchange format since JSON is the most common data interchange format availible currently. 
+Saves the pattern as a JSON object. This is intended to be useful as an interchange format since JSON is the most common data interchange format available currently. 
 
 
 #### Writing to PNG:
@@ -566,7 +566,7 @@ While there's only NONE, and THREE_SMALL for contingencies currently, both the t
 
 * The core units are 1/10th mm. This is what 1 refers to within most formats, and internally within pyembroidery itself. You are entirely permitted to use floating point numbers. When writing to a format, fractional values will be lost, but this shall happen in such a way to avoid the propagation of error. Relative stitches from position ( 0.0,  0.31 ) of (+5.4, +5.4), (+5.4, +5,4), (+5.4, +5,4) should encode as changes of 5,6 6,5 5,6. Taking the relative distance in the format as the integer change from the last integer position to the new one, maintaining a position as close to the absolute position as possible. All fractional values are considered significant. 
 
-In some read formats the formats themselves have a slightly different unit systems such as .PCD or .MIT these alternative units will be presented seemlessly as 1/10th mm units.
+In some read formats the formats themselves have a slightly different unit systems such as .PCD or .MIT these alternative units will be presented seamlessly as 1/10th mm units.
 
 ### Core Command Ordering
 

pyembroidery/EmbPattern.py

@@ -670,7 +670,7 @@ class EmbPattern:
                             self.stitches[last_change][2] = STOP
                         else:
                             thread_index += 1
-                    except IndexError:  # Non-existant threads cannot double
+                    except IndexError:  # Non-existent threads cannot double
                         return
                     init_color = False
             elif data == COLOR_CHANGE or data == COLOR_BREAK or data == NEEDLE_SET:

pyembroidery/EmbThreadPec.py

@@ -31,7 +31,7 @@ def get_thread_set():
         EmbThreadPec(246, 74, 138, "Deep Rose", "25"),
         EmbThreadPec(178, 118, 36, "Light Brown", "26"),
         EmbThreadPec(252, 187, 197, "Salmon Pink", "27"),
-        EmbThreadPec(254, 55, 15, "Vermillion", "28"),
+        EmbThreadPec(254, 55, 15, "Vermilion", "28"),
         EmbThreadPec(240, 240, 240, "White", "29"),
         EmbThreadPec(106, 28, 138, "Violet", "30"),
         EmbThreadPec(168, 221, 196, "Seacrest", "31"),
@@ -54,7 +54,7 @@ def get_thread_set():
         EmbThreadPec(247, 56, 102, "Carmine", "48"),
         EmbThreadPec(181, 75, 100, "Amber Red", "49"),
         EmbThreadPec(19, 43, 26, "Olive Green", "50"),
-        EmbThreadPec(199, 1, 86, "Dark Fuschia", "51"),
+        EmbThreadPec(199, 1, 86, "Dark Fuchsia", "51"),
         EmbThreadPec(254, 158, 50, "Tangerine", "52"),
         EmbThreadPec(168, 222, 235, "Light Blue", "53"),
         EmbThreadPec(0, 103, 62, "Emerald Green", "54"),